Merck Obtains Exclusive Rights to Market and Distribute
MassBiologics' Tetanus-Diphtheria (Td) Vaccine in the U.S.

Merck's Adult Vaccine Portfolio Now Includes 9 of the 10 Vaccines on
the U.S. CDC's Recommended Adult Immunization Schedule

April 21, 2010 07:30 AM Eastern Daylight Time

BOSTON & WHITEHOUSE STATION, N.J.--(BUSINESS WIRE)--MassBiologics (MBL) of the University of Massachusetts Medical School
and Merck & Co., Inc. (NYSE: MRK) announced today that they have entered
into an agreement that provides Merck with exclusive rights to market
and distribute MBL's tetanus and diphtheria toxoids adsorbed (Td)
vaccine in the United States, with the exception of Massachusetts, where
MBL will continue distributing the vaccine. Merck plans to begin
distributing the Td vaccine in June 2010. Specific financial details of
the agreement were not disclosed.

"Adult vaccination is an important element in Merck's commitment to help
people be well, and we are delighted to partner with MBL to add
tetanus-diphtheria vaccine to our broad U.S. portfolio of adult
vaccines," said Soren Bo Christiansen, M.D., senior vice president and
general manager, Adolescent & Adult Vaccines, Merck Vaccines. "This
agreement is another example of how Merck engages in partnerships that
will enable us to bring the most robust portfolio of products to our
customers."

MassBiologics' Td vaccine was licensed by the U.S. Food and Drug
Administration (FDA) in 1970. The vaccine is indicated for active
immunization for the prevention of tetanus and diphtheria and is
approved for use in people seven years of age and older.

The U.S. Centers for Disease Control and Prevention (CDC) recommends
that adults 19 years of age and older with an uncertain or incomplete
history of receiving the primary vaccination series of three doses of Td
vaccine should begin or complete the Td primary vaccination series, and
that adults who have not had a Td booster shot in 10 years or more
should be vaccinated. Adults 19 years of age and older should receive a
booster dose of Td vaccine every 10 years. Tdap (tetanus, diphtheria,
and acellular pertussis) vaccine should replace a single dose of Td for
adults aged 19–64 years who have not received a dose of Tdap previously,
to additionally help protect them against pertussis disease.

Tetanus and diphtheria can be serious diseases

Cases of tetanus and diphtheria have been drastically reduced in the
U.S. since the introduction of vaccines, but people can still be at risk
for these diseases. The bacteria that cause tetanus are found in soil
and can enter the body through any cut or wound. Tetanus is not spread
from person to person. Because tetanus bacteria are widespread in the
environment, vaccination is an important way to protect against tetanus.
Almost all cases of tetanus occur in people who have never been
vaccinated or who have not had a tetanus booster shot within the
preceding 10 years.

Tetanus, sometimes called "lockjaw," is a bacterial infection affecting
the nervous system. It causes severe muscle spasms that can lead to,
among other things, "locking" of the jaw so a person cannot open his/her
mouth or swallow. Symptoms include stiffness in the neck, rigidity of
abdominal muscles, difficulty with breathing and swallowing, and muscle
spasms can cause fractures of the spine and long bones. According to the
CDC, approximately 1 out of 5 cases of tetanus are fatal.

Diphtheria is rare in the U.S. due to widespread use of
diphtheria-containing vaccines; however, these bacteria are still a
concern. Diphtheria continues to occur in other parts of the world.
Diphtheria is caused by bacteria that can be passed from an infected
person to others by coughing or sneezing. Early symptoms of diphtheria
include sore throat, mild fever and chills. Usually the disease causes a
thick coating at the back of the throat that makes it difficult to
breathe or swallow, and may cause serious breathing problems. The most
common complications are inflammation of the heart that can lead to
abnormal heart rhythms, and inflammation of the nerves, which can cause
temporary paralysis of some muscles. Diphtheria bacteria not only
affects the throat, but can also infect other areas of the body, such as
the nose, eye, and skin.

Important information about tetanus-diphtheria vaccine

The tetanus diphtheria vaccine is contraindicated in patients with
hypersensitivity to any component of the vaccine or who have had a
severe allergic reaction after a previous dose of this vaccine or any
other Td vaccine.

Persons who experienced an Arthus-type hypersensitivity reaction
following a prior dose of a tetanus toxoid-containing vaccine usually
have high serum tetanus antitoxin levels and should not receive the Td
vaccine more frequently than every 10 years, even for tetanus
prophylaxis as part of wound management.

If Guillain-Barre Syndrome occurred within six weeks after receipt of a
previous dose of tetanus toxoid-containing vaccine, the decision to give
subsequent doses of the Td vaccine or any vaccine containing tetanus
toxoid should be based on careful consideration of the potential
benefits and possible risks.

The most common local adverse reactions associated with Td vaccine may
include erythema (redness), tenderness, and swelling at the injection
site. Common systemic reactions may include headache, malaise, and
temperature elevations.

Please see the accompanying Prescribing Information for Td vaccine.

About MassBiologics

MassBiologics is the only non-profit FDA-licensed manufacturer of
vaccines and other biologic products in the United States and produces
tetanus-diphtheria vaccine. MassBiologics traces its roots to 1894, and
since then has maintained a mission to improve public health through
applied research, development and production of biologic products.
MassBiologics has been a part of the University of Massachusetts Medical
School since 1997.

About the University of Massachusetts Medical School

The University of Massachusetts Medical School, one of the fastest
growing academic health centers in the country, has built a reputation
as a world-class research institution, consistently producing noteworthy
advances in clinical and basic research. The Medical School attracts
more than $240 million in research funding annually, 80 percent of which
comes from federal funding sources. The mission of the Medical School is
to advance the health and well-being of the people of the commonwealth
and the world through pioneering education, research, public service and
health care delivery with its clinical partner, UMass Memorial Health
Care. For more information, visit www.umassmed.edu.

About Merck

Today's Merck is a global healthcare leader working to help the world be
well. Merck is known as MSD outside the United States and Canada.
Through our prescription medicines, vaccines, biologic therapies, and
consumer care and animal health products, we work with customers and
operate in more than 140 countries to deliver innovative health
solutions. We also demonstrate our commitment to increasing access to
healthcare through far-reaching policies, programs and partnerships.
Merck. Be well. For more information, visit www.merck.com.

Forward-Looking Statement

This news release includes "forward-looking statements" within the
meaning of the safe harbor provisions of the United States Private
Securities Litigation Reform Act of 1995. Such statements may include,
but are not limited to, statements about the benefits of the merger
between Merck and Schering-Plough, including future financial and
operating results, the combined company’s plans, objectives,
expectations and intentions and other statements that are not historical
facts. Such statements are based upon the current beliefs and
expectations of Merck’s management and are subject to significant risks
and uncertainties. Actual results may differ from those set forth in the
forward-looking statements.

The following factors, among others, could cause actual results to
differ from those set forth in the forward-looking statements: the
possibility that the expected synergies from the merger of Merck and
Schering-Plough will not be realized, or will not be realized within the
expected time period, due to, among other things, the impact of
pharmaceutical industry regulation and pending legislation that could
affect the pharmaceutical industry; the risk that the businesses will
not be integrated successfully; disruption from the merger making it
more difficult to maintain business and operational relationships;
Merck’s ability to accurately predict future market conditions;
dependence on the effectiveness of Merck’s patents and other protections
for innovative products; the risk of new and changing regulation and
health policies in the U.S. and internationally and the exposure to
litigation and/or regulatory actions.

Merck undertakes no obligation to publicly update any forward-looking
statement, whether as a result of new information, future events or
otherwise. Additional factors that could cause results to differ
materially from those described in the forward-looking statements can be
found in Merck’s 2009 Annual Report on Form 10-K and the company’s other
filings with the Securities and Exchange Commission (SEC) available at
the SEC’s Internet site (www.sec.gov).

Prescribing Information for tetanus-diphtheria vaccine is attached.

TETANUS AND DIPHTHERIA TOXOIDS ADSORBED

Rx Only

DESCRIPTION

Tetanus and Diphtheria Toxoids Adsorbed (Td) manufactured by
MassBiologics is a sterile vaccine for intramuscular injection. After
shaking, the vaccine appears as a homogeneous milky white suspension.

Each 0.5 ml dose of MassBiologics’ Td is formulated to contain the
following active ingredients: 2 Lf of tetanus toxoid and 2 Lf of
diphtheria toxoid. Each 0.5 ml dose also contains aluminum adjuvant (not
more than 0.53 mg aluminum by assay), < 100 mcg (0.02%) of residual
formaldehyde, and a trace amount of thimerosal [mercury derivative, (≤
0.3 mcg mercury/dose)] (not as a preservative) from the manufacturing
process.

The Corynebacterium diphtheriae and Clostridium tetani
organisms are grown on modified Mueller's media1, 2 which
contains bovine extracts. The bovine material used in these extracts is
sourced from countries which the United States Department of Agriculture
has determined neither have nor present an undue risk for bovine
spongiform encephalopathy. Tetanus and diphtheria toxins produced during
growth of the cultures are detoxified with formaldehyde. The detoxified
materials are then separately purified by ammonium sulfate
fractionation. The diphtheria toxoid is further purified by column
chromatography. The tetanus and diphtheria toxoids are individually
adsorbed onto aluminum phosphate.

The tetanus and diphtheria toxoids induce at least 2 units and 1 unit of
antitoxin per ml of serum, respectively, in the guinea pig potency test.

CLINICAL PHARMACOLOGY

TETANUS

Tetanus (also known as lockjaw) is a serious, often fatal disease caused
by an extremely potent neurotoxin produced by C. tetani.

Protection against disease is due to the development of neutralizing
antibodies to tetanus toxin. A serum tetanus antitoxin level of 0.01
IU/ml measured via a neutralization assay is considered the minimum
protective level.3, 4 The efficacy against tetanus of
MassBiologics’ Td is supported by the following:

Response to primary series. Of 20 adults with less than 0.0025
units/ml of tetanus antitoxin in pre-immunization serum, 14 (70%) had
antitoxin concentrations of 0.01 or greater after 2 doses of Td (2 Lf
tetanus toxoid dose). After 3 doses of Td, 16 of 16 adults achieved
0.01 antitoxin units/ml.

Response to booster doses. Booster doses of Td at doses of 1 Lf and 5
Lf of tetanus toxoid induced tetanus antitoxin levels greater than
0.01 units/ml when administered to all 36 adults who had received
prior tetanus immunizations.5

DIPHTHERIA

Diphtheria is an acute toxin-mediated disease caused by toxigenic
strains of C. diphtheriae. Protection against disease is due to
the development of neutralizing antibodies to diphtheria toxin. A serum
diphtheria antitoxin level of 0.01 IU/ml is the lowest level giving some
degree of protection.3, 6 The efficacy against diphtheria of
MassBiologics’ Td is supported by the following:

Response to primary series. Of 10 adults with less than 0.001 units/ml
of diphtheria antitoxin in pre-immunization serum, 50% had antitoxin
concentrations of 0.01 or greater after 2 doses of Td (2 Lf diphtheria
toxoid dose). After 3 doses of Td, 6 of 6 adults achieved 0.01
antitoxin units/ml.

Response to booster doses. In clinical trials, booster doses of Td
formulated to contain 1 Lf and 5 Lf of diphtheria toxoid, both induced
antitoxin levels greater than 0.01 units/ml when administered to
adults with prior diphtheria immunity. 5, 7, 8 In 140
adolescent males given a single booster dose of the 1 Lf formulation,
all achieved an antitoxin titer of 0.01 units/ml or higher.8

INDICATIONS AND USAGE

MassBiologics’ Td is a vaccine indicated for active immunization for the
prevention of tetanus and diphtheria. This vaccine is approved for use
in persons 7 years of age and older.

CONTRAINDICATIONS

A severe allergic reaction (e.g., anaphylaxis) occurring after a
previous dose of this vaccine, or any other tetanus or diphtheria
toxoid-containing vaccine, or any component of this vaccine is a
contraindication to administration of MassBiologics’ Td vaccine. (See DESCRIPTION).
Because of the uncertainty as to which component of the vaccine might be
responsible, no further vaccination with diphtheria or tetanus
components should be carried out. Alternatively, such individuals may be
referred to an allergist for evaluation if further immunizations are to
be considered.

WARNINGS

FREQUENCY OF ADMINISTRATION

More frequent administration of MassBiologics’ Td than described in DOSAGE
AND ADMINISTRATION may be associated with an increased incidence and
severity of adverse reactions.

ARTHUS REACTIONS

Persons who experienced an Arthus-type hypersensitivity reaction
following a prior dose of a tetanus toxoid-containing vaccine usually
have high serum tetanus antitoxin levels and should not receive
MassBiologics’ Td more frequently than every 10 years, even for tetanus
prophylaxis as part of wound management. (See DOSAGE AND
ADMINISTRATION).

GUILLAIN-BARRÉ SYNDROME

A review by the Institute of Medicine found evidence for a causal
relation between tetanus toxoid and Guillain-Barré Syndrome.9
If Guillain-Barré Syndrome occurred within 6 weeks after receipt of a
previous dose of tetanus toxoid-containing vaccine, the decision to give
subsequent doses of MassBiologics’ Td or any vaccine containing tetanus
toxoid should be based on careful consideration of the potential
benefits and possible risks. 10

Vaccination with MassBiologics’ Td may not protect all individuals.

PRECAUTIONS

GENERAL

Epinephrine injection (1:1000) and other appropriate agents and
equipment must be immediately available should an acute anaphylactic
reaction occur.

Prior to the administration of MassBiologics’ Td, the vaccine
recipient’s current health status and health history should be reviewed.
This includes a review of the immunization history of the patient, the
presence of any contraindications to immunization, and any adverse
events after previous immunizations to allow an assessment of the
benefits and risks of vaccination. (See CONTRAINDICATIONS and WARNINGS).

If MassBiologics’ Td is administered to immunocompromised persons
(whether from disease or treatment) the expected immune response may not
be obtained.

INFORMATION FOR PATIENTS

Prior to administration of MassBiologics’ Td, patients, parents or
guardians should be informed by the health care provider of the benefits
and risks of immunization with Td and of the importance of completing
the primary immunization series or receiving recommended booster doses.

The health care provider should inform the patient, parent, or guardian
of the potential for adverse reactions that have been temporally
associated with MassBiologics’ Td or other vaccines containing similar
ingredients. Patients, parents or guardians should be instructed to
report any suspected adverse reactions to their health care provider.

According to the National Childhood Vaccine Injury Act of 1986, Vaccine
Information Statements must be provided by the health care provider with
each vaccine dose administered.10

DRUG INTERACTIONS

Patients who are on immunosuppressive therapy, including alkylating
agents, antimetabolites, cytotoxic drugs, irradiation, or
corticosteroids (used in greater than physiologic doses), may have a
reduced immune response to vaccines.

No safety and immunogenicity data are available on the concomitant
administration of MassBiologics’ Td vaccine with other U.S. licensed
vaccines.

CARCINOGENESIS, MUTAGENESIS, IMPAIRMENT OF FERTILITY

No studies have been performed with MassBiologics’ Td to evaluate
carcinogenicity, mutagenic potential, or impairment of fertility.

PREGNANCY CATEGORY C

Animal reproduction studies have not been conducted with MassBiologics’
Td. It is also not known whether MassBiologics’ Td can cause fetal harm
when administered to a pregnant woman or can affect reproduction
capacity. MassBiologics’ Td should be given to a pregnant woman only if
clearly needed.

NURSING MOTHERS

It is not known whether MassBiologics’ Td is excreted in human milk.
Because many drugs are excreted in human milk, caution should be
exercised when MassBiologics’ Td is administered to a nursing woman.

PEDIATRIC USE

MassBiologics’ Td is not approved for use in infants and children
younger than 7 years of age. The safety and effectiveness of
MassBiologics’ Td in this age group have not been established.

GERIATRIC USE

No studies have been performed with MassBiologics’ Td in adults aged 65
years and older in order to determine whether they respond differently
than younger subjects.

ADVERSE REACTIONS

DATA FROM CLINICAL TRIALS

Because clinical trials are conducted under widely varying conditions,
adverse reaction rates observed in the clinical trials of a vaccine
cannot be directly compared to rates in the clinical trials of another
vaccine, and may not reflect the rates observed in practice. However,
the adverse reaction information from clinical trials provides a basis
for identifying adverse events that appear to be related to vaccine use
and for approximating rates. Data on adverse reactions following fluid
and adsorbed preparations of MassBiologics’ Td with various doses of the
diphtheria and tetanus components have been reported in a series of
studies.5, 7, 8, 11, 12

POSTMARKETING REPORTS

The following adverse events have been identified during post-approval
use of MassBiologics’ Td. Because these reactions are reported
voluntarily from a population of uncertain size, it is not always
possible to reliably estimate their frequencies or to establish a causal
relationship to vaccination. The following adverse events were included
because of seriousness or frequency of reporting:

To report SUSPECTED ADVERSE REACTIONS, contact MassBiologics at
1-800-457-4626 or VAERS at 1-800-822-7967 or www.vaers.hhs.gov.

DOSAGE AND ADMINISTRATION

PRIMARY IMMUNIZATION

MassBiologics’ Td may be used in persons 7 years of age and older who
have not been previously immunized against tetanus and diphtheria, as a
primary immunization series consisting of three 0.5 ml doses. The first
two doses are administered 4-8 weeks apart and the third dose is
administered 6-12 months after the second dose.

MassBiologics’ Td may be used to complete the primary immunization
series for tetanus and diphtheria, following one or two doses of
Diphtheria and Tetanus Toxoids and Pertussis Vaccine Adsorbed
(whole-cell DTP), Diphtheria and Tetanus Toxoids and Acellular Pertussis
Vaccine Adsorbed (DTaP) and/or Diphtheria and Tetanus Toxoids Adsorbed
(DT) vaccine. However, the safety and efficacy of MassBiologics’ Td in
such regimens have not been evaluated.

ROUTINE BOOSTER IMMUNIZATION

MassBiologics’ Td may be used for routine booster immunization against
tetanus and diphtheria in persons 7 years of age and older who have
completed primary immunization against tetanus and diphtheria. Routine
booster immunization against tetanus and diphtheria is recommended in
children 11-12 years of age and every 10 years thereafter.10

The Advisory Committee on Immunization Practices (ACIP) has specific
recommendations on booster immunization against tetanus and diphtheria
for adolescents and adults.10, 13, 14

TETANUS PROPHYLAXIS IN WOUND MANAGEMENT

For active tetanus immunization in wound management of patients 7 years
of age and older, a preparation containing tetanus and diphtheria
toxoids is preferred instead of single-antigen tetanus toxoid to enhance
diphtheria protection.15 MassBiologics’ Td is approved for
wound management of patients 7 years of age and older.

The need for active immunization with a tetanus toxoid-containing
preparation, with or without Tetanus Immune Globulin (TIG) (Human)
depends on both the condition of the wound and the patient’s vaccination
history (Table 1).

When indicated, TIG (Human) should be administered using a separate
needle and syringe at a different anatomic site, according to the
manufacturer’s package insert. If a contraindication to using a tetanus
toxoid-containing vaccine exists in a person who has not completed
tetanus primary immunization and other than a clean, minor wound is
sustained, only passive immunization with TIG (Human) should be given.15

† The ACIP has specific recommendations on use of Td or Tetanus Toxoid,
Reduced Diphtheria Toxoids and Acellular Pertussis Vaccine Adsorbed
(Tdap) in adolescents and adults.13, 14

‡ If only three doses of fluid tetanus toxoid have been received, then a
fourth dose of toxoid, preferably an adsorbed toxoid, should be given.

§ Yes, if ≥ 10 years since the last tetanus toxoid-containing vaccine
dose.

¶ Yes, if ≥ 5 years since the last tetanus toxoid-containing vaccine
dose. (More frequent boosters are not needed and can accentuate side
effects.)

DIPHTHERIA PROPHYLAXIS FOR CASE CONTACTS

MassBiologics’ Td may be used for post-exposure diphtheria prophylaxis
in persons 7 years of age and older who have not completed primary
vaccination, whose vaccination status is unknown, or who have not been
vaccinated with diphtheria toxoid within the previous 5 years. Consult
ACIP recommendations for additional interventions for post-exposure
diphtheria prophylaxis.15

ADMINISTRATION

Shake the vial well to resuspend the vaccine before withdrawing the
dose. After shaking, MassBiologics’ Td is a homogenous milky white
suspension. Parenteral drug products should be inspected visually for
particulate matter and discoloration prior to administration, whenever
solution and container permit. If these conditions exist, MassBiologics’
Td should not be administered.

Inject 0.5 ml of MassBiologics’ Td intramuscularly. The preferred site
is the deltoid muscle. The vaccine should not be injected into the
gluteal area or areas where there may be a major nerve trunk.

Do not administer this vaccine intravenously, subcutaneously, or
intradermally.

MassBiologics’ Td should not be combined through reconstitution or mixed
with any other vaccine.

Centers for Disease Control and Prevention. Preventing tetanus,
diphtheria, and pertussis among adolescents: use of tetanus toxoid,
reduced diphtheria toxoid and acellular pertussis vaccines:
recommendations of the Advisory Committee on Immunization Practices
(ACIP). MMWR 2006;55(No. RR-3):1-43.

Centers for Disease Control and Prevention. Preventing tetanus,
diphtheria, and pertussis among adults: use of tetanus toxoid, reduced
diphtheria toxoid and acellular pertussis vaccine. Recommendations of
the Advisory Committee on Immunization Practices (ACIP) and
recommendation of ACIP, supported by the Healthcare Infection Control
Practices Advisory Committee (HICPAC), for use of Tdap among
health-care personnel. MMWR 2006;55(No. RR-17):1-37.

Centers for Disease Control and Prevention. Recommendations of the
Immunization Practices Advisory Committee (ACIP). Diphtheria, tetanus,
and pertussis: recommendations for vaccine use and other preventive
measures. MMWR 1991;40(No. RR-10):1-35.